1. Field of the Invention
The present invention relates to a projection lens for an imaging module. More particularly, the present invention relates to a projection lens adapted to adjust an aspect ratio of an image and an imaging module using the projection lens.
2. Descriptions of the Related Art
With the development of science and technology, various display devices have been developed in succession. Projectors, due to their capability of changing a size of an image according to a service place, have become indispensable products for displaying image information when enterprises hold meetings or people enjoy top level audio visual entertainment programs. However, to meet different demands of users in a more comprehensive way, projectors capable of selectively providing an image of different aspect ratios have gradually gained popularity among consumers.
Various optical structures have been developed in the art to enable an image projected by a projector to meet demands for different aspect ratios. Referring to FIG. 1, U.S. Pat. No. 5,930,050 discloses an anamorphic lens set 1 for displaying wide-screen images of different aspect ratios. The anamorphic lens set 1, which is of an independent optical mechanism, can be attached to an outer side of a projection lens 11 of a projection device through a slide rail. However, the anamorphic lens set 1 is disposed on a side of the projection lens 11 close to a screen 12 onto which an image is to be projected, and an angular range of light rays of the image has been expanded by the projection lens 11; therefore, if the light rays projected by the projection lens 11 are to be refracted completely and projected entirely onto the screen 12, the anamorphic lens set 1 must be made to have a large size, which indirectly adds to the overall weight. This makes it impossible to meet the demands for lightweight and slim projectors in the market.
Referring to FIG. 2, U.S. Pat. No. 7,289,272 discloses a projection lens 2 comprising an anamorphic lens set 21. Compared with the aforesaid anamorphic lens set 1, the anamorphic lens set 21 has a much smaller size. However, the projection lens 2 is actually an integrated lens set; i.e., it is suitable for display of only a single aspect ratio and fails to meet the demands for different image aspect ratios.
Accordingly, an urgent need still exists in the art to provide a projection lens that is light weight, has a small volume and can easily switch between different image aspect ratios to meet demands of users when watching different contents.